European patent applications can be filed in any language. However, if filed in a language other than an official language of the EPO (English, French or German), a translation into one of the official languages must be filed within two months of the date of filing (Rule 6(1)).

In the case of applications filed in "an admissible non-EPO language" (see below in A‑VII, 3.2), a reduction of the filing fee is allowed for certain categories of applicants (see A‑X, 9.2.1 and A‑X, 9.2.2).